In order to determine how EDN3 acts in neural crest melanocyte development, we are determining how exogenously added EDN3 alters the timing, number, survival and morphology of melanocytes in an in vitro system that we have developed. In order for melanocytes to differentiate in our in vitro system, several substances including TPA must be added to the cultures. We have found that EDN3 can successfully replace TPA in this system. We are currently exploring if related family members (EDN1 or EDN2) can substitute for EDN3 in this assay. We are also determining if the effect of EDN3 is dependent upon the presence of its receptor EDNRB on neural crest cells by using piebald mice as donors for the neural crest cultures. In addition, we are exploring whether neural crest obtained from the spotting mutations (piebald, lethal spotting, etc.) can be complemented using this system.